TUCSON, Ariz.  A U.S. Fish and Wildlife Service decision to designate 8.6 million acres in four western states as critical habitat for an endangered owl will stand, a federal judge has ruled.

U.S. District Judge Susan Bolton in Phoenix upheld the designation of critical habitat in Arizona, Utah, Colorado and New Mexico for the Mexican spotted owl despite an effort by the Arizona Cattle Growers' Association to overturn it.

Just under 4 million acres of habitat affected by the ruling is situated in Arizona, mostly in the northern part of the state. Also included is 2.2 million acres in Utah, 2.1 million acres in New Mexico and more than 322,000 acres in Colorado.

The designation is aimed at protecting the habitat from activities that remove forest cover, including logging, cattle grazing, urban sprawl or power lines, said Noah Greenwald, a conservation biologist for the Center for Biological Diversity, which intervened on behalf of Fish and Wildlife.

"We were disappointed, obviously," said association spokesman C.B. "Doc" Lane. "It's pretty bad, actually, that all of the endangered species stuff is done by litigation now. It isn't done rationally. But I suppose that's the way it has to be.

"The Mexican spotted owl habitat was established very hurriedly last time because of a court ruling, and we had to respond." He said association officials have not decided yet whether they will appeal Bolton's Feb. 1 ruling.

"This was a complete victory for the Mexican spotted owl," Matt Kenna (Ken-AY), attorney for the Western Environmental Law Center, which represented the Center for Biological Diversity, said in a statement.

"The Mexican spotted owl will continue to get the habitat protection it needs to survive and recover," Greenwald added. "To save endangered species, we have to protect the places they call home."

All the cattle growers' arguments were rejected, he said.

A critical habitat designation requires federal agencies to make certain that projects which fall under their purview do not imperil endangered species or negatively change their most vital habitat.

"The environmental community has figured out that when an agency doesn't do something -- crossing the T's or dotting the I's -- they can always win in court," Lane said. "So that's the way it's functioning now."

But Greenwald said the ruling means the spotted owl, listed as endangered in 1992, has a chance at recovery.

"Critical habitat provides an absolutely essential tool to save the owl and the forest habitats it depends on," Greenwald said.

Having critical habitat will ensure that U.S. Forest Service logging does not limit the bird's recovery or drive it into extinction, the center said.

In a published study, it found that the likelihood of a troubled species' status improving more than doubled with critical habitat.

Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.